Add pod condition PodScheduled to detect situation

when scheduler tried to schedule a Pod, but failed.

Ref #24404

pkg/api/types.go

@@ -1058,6 +1058,8 @@ type PodConditionType string
 
 // These are valid conditions of pod.
 const (
+	// PodScheduled represents status of the scheduling process for this pod.
+	PodScheduled PodConditionType = "PodScheduled"
 	// PodReady means the pod is able to service requests and should be added to the
 	// load balancing pools of all matching services.
 	PodReady PodConditionType = "Ready"